Woven prosthesis and method for manufacturing the same

ABSTRACT

A woven prosthesis, such as a woven vascular graft, woven from warp and weft yarns. Velour warp yarns forming the prosthesis are selectively incorporated into a base layer of the prosthesis so as to provide a bulbous section without compromising the porosity of the prosthesis.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an implantable woven prosthesis and amethod for manufacturing same. In an exemplary embodiment, theprosthesis is a tubular graft varying in diameter along its length. Theprosthesis may be used, for example, by vascular or cardiovascularsurgeons, for repairing portions of the cardiovascular system, includingbut not limited to all or portions of the ascending aorta, and aorticroot. In an exemplary embodiment, the present invention may alsoapplicable to valve sparing and Bentall-type procedures.

2. Description of Related Art

Tubular woven fabrics have been used for soft-tissue implantableprostheses to replace or repair damaged or diseased lumens in the body.Within the field of cardiothoracic surgery, for example, endoprosthesesare used in the vascular system to prevent blood flow and pressure fromrupturing a weakened or otherwise damaged section of the vessel. Suchendoluminal conduits may be affixed in a specified location in thevessel by means of stents, hooks, sutures, or other mechanisms servingto secure the devices in place. Endoluminal tubular devices or conduitscan also be used in other lumens in the body, such as in the esophagusand colon areas.

One area of specialty, replacement or repair of the aortic valve and/orthe ascending aorta, in particular the sinuses of Valsalva, involvesspecialized and time consuming surgical procedures. These procedureshave traditionally been performed with straight woven grafts. Althoughthe procedures can be executed with a straight graft prosthesis, thereis an increasing perception within the surgical community that vasculargrafts incorporating bulges or bulbous portions to mimic the naturalshape and profile of the human vasculature may be beneficial. Attemptsto fabricate such grafts by others typically have caused problems in oneor both of the areas of fabrication, surgical utility, and/or postoperative patency.

For example, some fabrication attempts have involved post-weavingprocessing such as stitching, suturing, or the seaming of cut sectionsof corrugated fabrics together in a manner that results in a graftcomprising a corrugated expandable middle section. Such a graft requiresadditional and costly manufacturing steps. Furthermore, the resultinggraft can compromise surgical utility and ease of use for the surgeon,since a sufficiently flat and smooth surface is not provided foranastomosis to occur on a bulbous portion. Such deficiencies complicateanastomosis procedures.

Additionally, the “seams” or “junctions” where the multiple componentsare brought together create localized portions of graft rigidity,strength, and change in porosity not found in other portions of thegraft. The resulting non-uniform nature of the underlying graft forcesthe surgeon to consider orientation of the graft prior to and duringimplantation and/or anastomosis. This extra precaution required of thesurgeon may distract him or her from other aspects of the surgery.

Furthermore, in vivo arterial pressure applied to grafts with corrugatedbulbous sections may result in expanded shapes and dimensions that aredrastically different when compared to the unpressurized state of suchprosthesis commonly occurring during surgery. With such prostheses, thesurgeon will therefore not be able to predict the in vivo performance ofthe prosthesis in terms of the clearance or engagement of valve leafletswith the inner sidewall of the prosthesis. Therefore, the surgeon maynot fully appreciate how such a graft will function in vivo, and may nothave any predictions as to long-term surgical success of the prostheticthereby potentially jeopardizing the intended efficacy of the surgicalprocedure.

Other examples of fabricating prostheses for addressing problemsrelating to the ascending aorta and sinuses of Valsalva attempt toutilize shrinking characteristics of yarns in a controlled manner suchthat smaller diameter portions of a graft are created through theshrinking of weft yarns. While tapers may be able to be formed throughsuch a procedure, concerns relating to suture retention strength as wellas non-uniform porosity of the fabric structure can cause problems forsurgeons and/or long term durability of the prosthesis, when used forrepairing portions of the ascending aorta. Additionally, the fabricatorof such prostheses will be limited through the shrink coefficients ofthe yarns to design geometries of sufficient taper required formimicking the sinuses of Valsalva.

SUMMARY OF THE INVENTION

An implantable prosthesis according to an example embodiment of thepresent invention comprises a woven base comprising base warp yarnsinterwoven with weft yarn passes, the woven base at least partiallyforming smaller and larger diameter portions of the prosthesis and oneor more velour yarns forming part of both the smaller and largerdiameter portions. In at least a portion of the larger diameter portionat least one of the one or more velour yarns incorporated into the wovenbase and exhibiting a weave pattern consistent with the woven base.

According to an example embodiment, within the smaller diameter portion,the at least one of the one or more velour yarns is not incorporatedinto the woven base and does not exhibit a weave pattern consistent withthe woven base.

According to an example embodiment, a spacing between the base warpyarns is maintained approximately the same in the smaller and largerdiameter portions without adding additional warp yarns to the largerdiameter portion beyond that in the smaller diameter portion.

According to an example embodiment, an increase in diameter of theprosthesis going from the smaller diameter portion to the largerdiameter is effected by increasing spacing between the base warp yarnsduring weaving of the prosthesis.

According to an example embodiment, the spacing between the base warpyarns in the larger diameter portion is made smaller without reducing adiameter of the larger diameter portion by at least one of the one ormore velour yarns incorporated into the woven base of the largerdiameter portion.

According to an example embodiment, the prosthesis is a generallytubular graft and the larger diameter portion lies within a portion ofthe graft varying in diameter along a longitudinal axis of the graft andthe smaller diameter portion lies within a portion of the graft having agenerally uniform diameter.

According to an example embodiment, the prosthesis is a generallytubular graft and the larger and smaller diameter portions lie within aportion of the prosthesis varying in diameter along a longitudinal axisof the graft.

According to an example embodiment, in at least a portion of the smallerdiameter portion the one or more velour yarns exhibit a float that isentirely absent or smaller in the larger diameter portion.

According to an example embodiment, a spacing between the base warpyarns in the smaller diameter portion is within 30% of the size of thespacing in the larger diameter portion.

According to an example embodiment, a spacing between the base warpyarns in the smaller diameter portion is within 15% of the size of thespacing in the larger diameter portion.

According to an example embodiment, a spacing between the base warpyarns in the smaller diameter portion is within 10% of the size of thespacing in the larger diameter portion.

According to an example embodiment, the prosthesis comprises a quantityof the base warp yarns and velour yarns is the same in the largerdiameter portion as the smaller diameter portion, and wherein the basewarp yarns and the velour warp yarns are continuously woven between thesmaller diameter portion and the larger diameter portion.

According to an example embodiment, the prosthesis comprises a secondarywoven layer disposed over at least one of the smaller and largerdiameter portions, and a portion of a yarn forming the secondary layeris incorporated into the base layer of the larger portion.

An implantable prosthesis according to an example embodiment of thepresent invention comprises, (i) a woven structure comprising warp yarnsinterwoven with weft passes, all or a portion of the warp yarns togetherwith the weft passes form a woven base of the woven structure, (ii) afirst portion of the woven structure is woven with a first set of thewarp yarns, a first subset of the first set of the warp yarns interwovenwith the weft passes forms the woven base in the first portion, two ofthe warp yarns in the first subset in the first portion are spaced apartfrom each other a first distance along a surface of the prosthesis, thefirst distance is greater than any spacing between any other pair ofwarp yarns in the first subset in the first portion along the surface ofthe prosthesis, (iii) a second portion of the woven structure is wovenwith the first set of the warp yarns, a second subset of the first setof the warp yarns interwoven with the weft passes forms the woven basein the second portion, two of the warp yarns in the first subset in thesecond portion are spaced apart from each other a second distance alongthe surface of the prosthesis, the second distance is greater than anyspacing between any other pair of warp yarns in the first subset in thesecond portion along the surface of the prosthesis. The second distanceis greater than the first distance, and the number of warp yarns in thefirst subset is smaller than the number of warp yarns in the secondsubset.

According to an example embodiment the portion of the warp yarnsinterwoven with the weft passes and disposed in the woven base arearranged in a base weave pattern, and another portion of the warp yarnsnot disposed in the woven base are velour warp yarns.

According to an example embodiment the prosthesis is a generally tubulargraft, the first portion having a first diameter along a longitudinalaxis of the graft, the second portion having a second diameter along thelongitudinal axis larger than the first diameter.

According to an example embodiment the first portion of warp yarns notin the first subset forming the woven base exhibit a float that isentirely absent or smaller in the second portion.

According to an example embodiment, the prosthesis has a first end and asecond end, and essentially all the warp yarns are continuously wovenbetween the first and second ends.

According to an example embodiment the prosthesis comprises a secondarywoven structure disposed over at least one of the first and secondportions, wherein a portion of a yarn forming the secondary wovenstructure is incorporated into the woven base of the secondary portion.

An example method for making a prosthesis according to the presentinvention comprises the steps of, (i) weaving a woven base from a set ofwarp yarns and at least one weft yarn pass the set of warp yarnscomprises warp yarns woven as base warp yarns and warp yarns woven asnon-base warp yarns, wherein the base warp yarns and weft yarn passesare woven into a base weave pattern, and the non-base warp yarns arewoven with at least one weft yarn pass when not woven into a base weavepattern, (ii) incorporating into the woven base one or more of thenon-base warp yarns, wherein the one or more non-base warp yarns assumea weave pattern consistent with all or portions of the base weavepattern.

According to an example embodiment the non-base warp yarns are velouryarns.

According to an example embodiment the woven base is configured toestablish a smaller and larger diameter portion, and the larger diameterportion is capable of achieving a larger diameter than the smallerdiameter portion. The larger diameter of the larger diameter portion isachieved by the step of incorporating into the woven base one or morevelour yarns.

An example method for making the graft may further include the step ofincorporating into the woven base one or more velour yarns exclusivelyutilizes velour yarns utilized as velour prior to being incorporatedinto the base weave pattern.

According to an example embodiment the larger diameter portion has abase warp density within a tolerance of 30% of a base warp density forthe smaller diameter portion.

According to an example embodiment the larger diameter portion has abase warp density within a tolerance of 15% of a base warp density forthe smaller diameter portion.

According to an example embodiment the larger diameter portion has abase warp density within a tolerance of 10% of a base warp density forthe smaller diameter portion.

According to an example embodiment a variable reed is moved during theweaving step to provide for a varied diameter profile of the medicalprosthesis.

An example method for making a prosthesis according to the presentinvention comprises the step of weaving a woven base comprising basewarp yarns interwoven with weft yarn passes, the base at least partiallyforming smaller and larger diameter portions, and one or more velouryarns forming part of both the smaller and larger diameter portions. Theexample method for making the prosthesis may further comprise weaving inat least a portion of the larger diameter portion at least one of theone or more velour yarns into the woven base to exhibit a weave patternconsistent with the woven base.

According to an example embodiment the at least one of the one or morevelour yarns woven into the woven base of the larger diameter portionand exhibiting a weave pattern consistent with the woven base is notwoven into the base of the smaller diameter portion.

An example method for making a prosthesis according to the presentinvention comprises the steps of, (i) weaving a variable diameter grafthaving a velour layer on at least a portion of the graft, comprising thestep of changing a weave pattern of a warp yarn used to form the velourlayer in a smaller diameter portion of the graft such that said warpyarn takes on a weave pattern and forms part of a base layer of a largerdiameter portion of the graft.

An example method for making the prosthesis may further include the stepof changing the weave pattern of the warp yarn as it transitions fromthe larger diameter portion to a second smaller diameter portion so asto form a velour layer on at least a portion of the second smallerdiameter portion which is smaller in diameter than the larger diameterportion.

An example method for making the prosthesis may further include the stepof shifting at least a pair of adjacent warp yarns used to form a baselayer of the smaller diameter portion so as to increase a spacingbetween the adjacent warp yarn in the larger diameter portion.

According to an example embodiment a spacing between base warp yarnsused to form the smaller diameter portion is within 30% of the size of acorresponding spacing between the same base warp yarns in the largerdiameter portion.

According to an example embodiment a spacing between base warp yarnsused to form the smaller diameter portion is within 15% of the size of acorresponding spacing between the same base warp yarns in the largerdiameter portion.

An example method for making a prosthesis according to the presentinvention comprises the steps of, (i) forming a first portion of theprosthesis by interweaving base warp yarns, velour warp yarns, and oneor more weft yarn passes, (ii) shifting at least a pair of adjacent basewarp yarns so as to increase or decrease a spacing between them, and(iii) forming a base layer of a second portion of the prosthesis byweaving the one or more weft yarn passes with the at least a pair ofshifted base warp yarns together with one or more of the velour warpyarns.

According to an example embodiment wherein the velour warp yarn exhibitsa float in the first portion and no float or less of a float in thesecond portion.

According to an example embodiment, wherein the shifting is accomplishedusing a warp yarn guide device.

According to an example embodiment, the warp yarns pass through gaps inthe warp yarn guide device and the spaces are spaced apart a distancegreater than the spacing between the warp yarns in the first portion ofthe prosthesis.

According to an example embodiment, wherein the medical prosthesis is agenerally tubular graft and the second portion of the graft has a largerdiameter than the first portion of the graft.

According to an example embodiment, the shifting is incrementallyincreased or decreased along a longitudinal axis of the graft so as toeffect a change in diameter of the prosthesis.

According to an example embodiment, wherein a spacing between the basewarp yarns in the first portion is within 30% of the size of acorresponding spacing between the same base warp yarns in the secondportion.

An example method for making the graft may further include the step ofusing at least one of the base warp yarns from the first portion in thesecond portion as a velour warp yarn and not as part of the base layerof the second portion.

According to an example embodiment, a quantity of the base warp yarnsand velour warp yarns is the same for both the first portion and thesecond portion.

According to an example embodiment a quantity of the base warp yarns andvelour warp yarns is consistent throughout the entire medicalprosthesis.

An example method for weaving a prosthesis according to the presentinvention comprises the steps of, (i) weaving a woven base comprisingbase warp yarns interwoven with weft yarn passes, the base at leastpartially forming smaller and larger diameter portions of theprosthesis, one or more velour yarns forming part of both the smallerand larger diameter portions, and (ii) incorporating in at least aportion of the larger diameter portion at least one of the one or morevelour yarns into the woven base so as to exhibit a weave patternconsistent with the woven base. According to an example embodiment,incorporating in step (ii) may not be in the smaller diameter portion.

An example method for weaving the prosthesis may further include thestep of shifting at least a pair of adjacent warp yarns used to form abase layer of the smaller diameter portion so as to increase a spacingbetween said adjacent warp yarns in the larger diameter portion.

An example method for making an implantable medical prosthesis accordingto the present invention and comprising a woven structure comprisingwarp yarns interwoven with weft passes, all or a portion of the warpyarns together with the weft passes form a woven base of the wovenstructure, comprises the steps of, (i) weaving a first portion of thewoven structure with a first set of the warp yarns, a first subset ofthe first set of the warp yarns interwoven with the weft passes formsthe woven base in the first portion, two of the warp yarns in the firstset in the first portion are spaced apart from each other a firstdistance along a surface of the prosthesis, the first distance isgreater than any spacing between any other pair of warp yarns in thefirst set in the first portion along the surface of the prosthesis, and(ii) weaving a second portion of the woven structure with the first setof the warp yarns, a second subset of the first set of the warp yarnsinterwoven with the weft passes forms the woven base in the secondportion, two of the warp yarns in the first set in the second portionare spaced apart from each other a second distance along the surface ofthe prosthesis, the second distance is greater than any spacing betweenany other pair of warp yarns in the first set in the second portionalong the surface of the prosthesis.

An implantable prosthesis according to an example embodiment of thepresent invention comprises (i) a woven base comprising base warp yarnsinterwoven with weft yarn passes, the base at least partially formingsmaller and larger diameter portions of the prosthesis, and (ii) one ormore additional warp yarns forming part of both the smaller and largerdiameter portions. In at least a portion of the larger diameter portionbut not the smaller diameter portion at least one of the one or moreadditional warp yarns incorporated into the woven base and exhibiting aweave pattern consistent with the woven base.

An implantable prosthesis according to an example embodiment of thepresent invention comprises a prosthesis comprising a woven base, thebase forming all or part of the sidewall of a proximal tubular portion,a larger diameter portion, and a distal tubular portion, the largerdiameter portion comprises a maximum diameter, the maximum diameter is 4or more millimeters larger than a measured diameter within the proximaltubular portion, the larger diameter portion has a length betweenseventy five percent and one hundred fifty percent of the measureddiameter within the proximal tubular portion, the proximal tubularportion and the larger diameter portion have a substantially uniformyarn to yarn spacing within the woven base for warp yarns woven withweft passes within the woven base.

According to an example embodiment the weft passes are woven with thesame yarn material and shrinkage attributes throughout the proximaltubular portion, the larger diameter portion, and the distal tubularportion. The shrinkage attributes include coefficients of shrinkage.

According to an example embodiment the weft passes are woven with thesame weft yarn throughout the proximal tubular portion, the largerdiameter portion, and the distal tubular portion.

According to an example embodiment the larger diameter portion isseamlessly woven with the proximal tubular portion and the distaltubular portion.

According to an example embodiment the same quantity of warp yarns areused to form the proximal tubular portion, the larger diameter portion,and the distal tubular portion.

According to an example embodiment the larger diameter portion isconfigured to be dimensionally stable under pressurized conditions of120 millimeters of Mercury.

According to an example embodiment the larger diameter portion isconfigured to maintain its diameter under fluidic pressurized conditionsof 120 millimeters of Mercury.

According to an example embodiment the woven base at the maximumdiameter of the larger diameter portion is free of at least one ofcorrugations, pleats, and crimps.

According to an example embodiment the larger diameter portion isdimensionally stable under pressurized conditions of 120 millimeters ofMercury.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is perspective view of a vascular graft according to an exampleembodiment of the present invention.

FIG. 2 is a cross sectional view taken along lines 2-2 in FIG. 1.

FIG. 3 is a cross sectional view taken along lines 3-3 in FIG. 1.

FIG. 4A is a partial sectional view of a portion of the graft of FIG. 2.

FIG. 4B is a partial sectional view of a portion of the graft in FIG. 3.

FIG. 5 is a magnified top view of a portion of the graft surface in FIG.1.

FIG. 6 is a sectional view taken along lines 6-6 in FIG. 5.

FIG. 7 is a sectional view taken along lines 7-7 in FIG. 6.

FIG. 8 is an elevation view of a vascular graft according to an exampleembodiment the present invention.

FIG. 9 is a magnified view of a bulbous portion and adjacent portions ofthe graft of FIG. 8.

FIG. 10 is a magnified view taken of a portion of the graft as shown inFIG. 8 and FIG. 9.

FIG. 11 is a magnified view of a sub-portion of the portion illustratedin FIG. 10.

FIG. 12A is a sectional view taken along lines 12A-12A in FIG. 10.

FIG. 12B is a sectional view taken along lines 12B-12B in FIG. 10.

FIG. 12C is a sectional view taken along lines 12C-12C in FIG. 10.

FIG. 13A is an elevation view of a fan-shaped reed in a first position.

FIG. 13B is an elevation view of a fan-shaped reed in a second position.

FIG. 13C is an elevation view of a fan-shaped reed in a third position.

FIG. 14A is an elevation view of a fan-shaped reed in a first position.

FIG. 14B is an elevation view of a fan-shaped reed in a second position.

FIG. 14C is an elevation view of a fan-shaped reed in a third position.

FIG. 15 is a magnified view of a portion of the graft in FIG. 8.

FIG. 16A is a perspective view of a graft according to an exampleembodiment of the present invention.

FIG. 16B is an elevation view of the graft of FIG. 16A.

FIG. 17A is a perspective view of a graft according to an exampleembodiment of the present invention.

FIG. 17B is an elevation view of the graft of FIG. 17A.

FIG. 18 is a front view of a fan-shaped reed.

FIG. 19A is an overhead view of a weaving station according to anexample embodiment of the present invention.

FIG. 19B is a side view of the weaving station of FIG. 19A.

FIG. 20 is an elevation view of a graft according to an exampleembodiment of the present invention.

FIG. 21 is an elevation view of a graft according to an exampleembodiment of the present invention.

FIG. 22 is an elevation view of a graft according to an exampleembodiment of the present invention.

FIG. 23 is an elevation view of a graft according to an exampleembodiment of the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

For purposes of the description hereinafter, the words “upper,” “lower,”“right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” “lateral,”“longitudinal,” “axial,” and like terms, if used, shall relate to theinvention, as it is oriented in the drawing figures. When appropriate,the term “proximal” shall refer to the relative location of an aspect ofa prosthesis, directed towards a heart such as a human heart, and theterm distal shall refer to a relative location of an aspect ofprosthesis in a direction away from a heart. It is to be understood thatthe invention may assume many alternative variations and embodimentsexcept where expressly specified to the contrary. It is also to beunderstood that the specific devices and embodiments illustrated in theaccompanying drawings and described herein are simply exampleembodiments of the invention.

FIG. 1 illustrates a varied-diameter prosthesis 10 according to anexample embodiment of the present invention configured, for example, asa replacement for the aortic root or ascending aorta. Prosthesis 10includes a first woven tubular portion 12, a bulbous second wovenportion 14, and a third woven tubular portion 16. Prosthesis 10 furthercomprises a proximal end 18, a distal end 20, and a sidewall 30 disposedtherebetween. The sidewall 30 is continuously woven thereby usingcontinuous warp yarns between the ends of the woven structure, such asthe proximal 18 and distal end 20 without the need for cutting apart orwelding together the warp yarns in between the ends. Other exampleconfigurations of the prosthesis 10 are illustrated in FIGS. 8, 16A,16B, 17A, 17B, and 20 to 23.

The sidewall 30 of prosthesis 10 shown in FIG. 1 is configured to resista predetermined level of blood leakage. The leakage rate may becontrolled by adjusting the porosity of the sidewall 30 by, for example,adjusting the weave pattern, yarn spacing, yarn denier, and/or yarntightness. Such attributes of sidewall 30 will provide for a uniformporosity sufficient to provide for tissue ingrowth, yet not cause orpromote leakage. The porosity of sidewall 30 can be generally uniformthroughout prosthesis 10 before and/or after an optional coatingapplication. Coating applications including collagen or gel coatings maybe employed depending on the desired configuration by the fabricator.Desirably, a porosity of sidewall 30 after a coating step may be lessthan 5 milliliters per centimeter squared per minute at 120 mm Hg. Thismay be measured using the Wesolowski method.

A variety of weave patterns may be employed. When warp yarns of thepresent disclosure engage consecutive weft passes, this is commonlyknown as a plain weave pattern. Additionally, when warp yarns skip,jump, or float over a plurality of weft passes (greater than the skiputilized in the base), these warp yarns are referred as to velour warpyarns and the weave pattern is referred to as a velour weave pattern. Avariety of weave patterns may be chosen for both the base as well asportions other than the base, such as warp yarn patterns for those warpyarns not in the base. Examples of non-base warp yarn patterns includevelour weave patterns for warp yarns not in the base. Velour weavepatterns may include single velour, double velour, and others.Generally, the frequency of interlacing of weft pass is greater for warpyarns when in the base it is for warp yarns when in a non-base layersuch as a velour layer.

Prosthesis 10 is generally elongate, and is woven with warp yarnsarranged generally parallel to an axis 34 shown in FIG. 1. First andsecond tubular portions 12 and 16 are shown as straight tubular portionsand are continuously interwoven with the bulbous portion 14 disposedbetween the tubular portions 12 and 16. The prosthesis 10, 10,′ 10,″10,′″ 310, 410, 510, 610 depicted in FIGS. 1, 8, 16A, 16B, 17A, 17B, and20 to 23 represents just a few examples of the universe of complexcontoured vascular prosthetic structures capable of being producedutilizing the techniques of the present invention, and other variationswithin the scope of the claimed invention are contemplated.

FIG. 2 illustrates a highly schematic cross section taken about line 2-2in FIG. 1. The diameter of the prosthesis 10 at line 2-2 is labeledusing reference number 32. As discussed further below, the prosthesis 10as illustrated in FIG. 2 has already undergone processing steps so as toallow it to maintain this substantially self-supporting configuration.Prior to this processing, the prosthesis has a more flattened profilecommon to greiges.

FIG. 3 illustrates a highly schematic cross section taken about line 3-3in FIG. 1. The diameter of the prosthesis 10 at line 3-3 is labelledusing reference number 33. Line 3-3 intersects prosthesis 10 at a largerdiameter than line 2-2, and thus the diameter 33 is larger in magnitudethan the diameter 32.

FIG. 4A is a magnified view of a circumferential section 35 ofprosthesis 10 shown in FIG. 2. Illustrated is a cross section of thesidewall, comprising a total of fifteen warp yarns 40, and two weftpasses 52. A first set of warp yarns (fifteen as illustrated) are shown,ten of which are interwoven with a first set of weft passes 52 (two weftyarns as shown), and comprise a first subset of the first set or baselayer 60. The term “base” is meant to be interchangeably used with theterms “base layer,” “foundation,” “ground” or “ground layer.” Theremaining warp yarns make up a second set of warp yarns, and arepositioned outside the base layer 60, in a non-base layer, such as avelour layer 62. This second set comprises among the five non-base warpyarns, yarns 27,′ 29,′ and 31.′ In this embodiment, the non-base velourlayer provides a loose weave (relative to the base layer 60) allowingfor tissue ingrowth into the prosthesis 10 during usage as a vascularconduit and, thus, functions as a velour layer.

Similar to FIG. 4A, FIG. 4B represents a magnified view of acircumferential section 37 of prosthesis 10 shown in FIG. 3 taken overthe same arc as section 35. Illustrated is a cross section of thesidewall, including a total of thirteen warp yarns 40, and two weftpasses 52. A first set of warp yarns 40 (thirteen as illustrated) areshown, ten of which are interwoven with a first set of weft passes 52(two weft yarns as shown), and comprise a first subset of the first setor base layer 60. Two warp yarns of the first subset of the first setare warp yarns 27″ and 31,″ which are the same warp yarns 27′ and 31′illustrated in FIG. 4A, but now positioned in FIG. 4B as interwoven withweft passes 52 and in the base layer 60. The two warp yarns 27 and 31have therefore have been shifted from a first position in a non-baselayer (velour layer 62) illustrated in FIG. 4A (as warp yarns 27′ and31′), to a base layer 60 illustrated in FIG. 4B (as warp yarns 27″ and31″).

Despite the diameter increase between FIG. 2 and FIG. 3, it should benoted that a center-to-center distance or spacing 3 between adjacentwarp yarns 40 in both FIGS. 4A and 4B is the same or approximately thesame. The expanded diameter in the bulbous portion 14, therefore, doesnot come at the expense of increased prosthesis porosity in this portion14, which can cause blood leakage as well as reduce suture integrityduring procedures such as anastomosis. Rather, shifting warp yarns 27′and 31′ in the non-base layer 62 into the base layer 60 during weavingof the prosthesis 10 allows for an increased diameter in the secondwoven portion 14 while still maintaining the yarn density, and thusporosity of the prosthesis 10, in this portion 14. Shifting the warpyarns 40 apart, absent any other intervention, necessarily decreases theyarn density of the prosthesis 10 in the bulbous portion 14.

In an exemplary embodiment, rather than shifting both yarns 27′ and 31′into the base layer 60, only one of yarns 27′ and 31′ may be shiftedinto the base layer. In this case, spacing between adjacent warp yarnswill increase compared to that in shown in FIGS. 4A and 4B. This may bedesirable to the extent a reduced porosity is desired in the bulboussecond portion 14 as compared to, for example, the first woven tubularportion 12, while still maintaining the porosity above a level allowingfor blood leakage.

Throughout the present disclosure, including FIGS. 4A and 4B, when thewarp yarns are located in a base layer of the prosthesis and haveadopted a weave pattern or first weave pattern consistent with the baselayer, the warp yarns when in the base layer 60 are referred togenerically as base warp yarns. Furthermore, when the warp yarns are notin the base layer 60 and have not adopted the weave pattern of the baselayer 60, or have adopted a second weave pattern different from thefirst weave pattern, the warp yarns may be referred to within thepresent disclosure as non-base warp yarns, such as, but not limited tovelour warp yarns. Some warp yarns may be positioned and/or woven as abase warp yarn throughout all or just a portion of the entire prostheticstructures described herein. Some warp yarns may be positioned and/orwoven as a velour warp yarn throughout all or just a portion of theprosthetic structures described herein. Further, some warp yarns mayserve as both velour warp yarns and base warp yarns and may transitionbetween the two states by a transition or adjustment in weave pattern,or frequency of interlacing.

FIG. 5 is a magnified view of a portion 46 (circumscribed in dashedlines for reference only) of an external surface 28 of prosthesis 10 asshown in FIG. 1. Three warp yarns (generally referenced as warp yarns40) are shown woven with a plurality of weft passes 52. The warp yarnsextend in a direction correlating to arrows 48, while the weft passes 52extend in directions that correlate with arrows 50. Other directions maybe employed without departing from the spirit of the invention, and thedirections shown are merely illustrative. Arrows 48 are generallyconsistent with the axis 34 in FIG. 1.

Of the warp yarns 40 illustrated in FIG. 5, two of the warp yarns 40 arebase warp yarns 42 throughout the entire figure, and one of the warpyarns 44 exhibits behaviours of both a base warp yarn, such as warpyarns 42, as well as a non-base warp yarn, such as a velour warp yarn.The non-base warp yarn 44 exhibits both a first weave pattern, i.e., a5/1 velour pattern, and a second weave pattern, i.e., a 1/1 plain weavepattern. In the 5/1 velour pattern, the warp yarn 44 (shown crosshatched for illustrative purposes only) passes under a first weft pass52 (first to the left in FIG. 5), and floats over five subsequent weftpasses 52 before passing under the third to last right most weft pass52. After passing under the third to last right most weft pass 52, warpyarn 44 transitions to a base warp yarn by adopting a repeating over andunder 1/1 plain weave pattern for the remaining weft passes 52.

Consistent with the above, base warp yarns 42 a and 42 b engage each ofthe nine subsequent weft passes 52 from left to right. Specifically,base warp yarn 42 a is positioned below the first weft pass while basewarp yarn 42 b is positioned above the first weft pass. This patternrepeats such that all of the nine weft passes shown in FIG. 5 areinterwoven with the first and second base warp yarns 42 a, 42 b.

On the right most side of portion 46, where warp yarn 44 iswoven/incorporated into the base 60, and adopts a weave patternconsistent with the base (such as the 1/1 weave pattern shown for basewarp yarns 42 a, 42 b), adjacent base warp yarns 40 are shifted apartfrom each other in the base layer 60 and accommodate this incorporation.This relative shifting of the base warp yarns 40 in the base layer 60 asillustrated occur before the transition in weave pattern but may alsooccur at or after the transition in weave patterns. As detailed below, awarp yarn guide device (FIGS. 13A-13C and 14A-14C), such as a fan-shapedreed, may be used to adjust the spacing between the warp yarns 40. Whenwarp yarn 44 is moved into the base layer 60, warp yarn 44 adopts thesame weave pattern as one or both of base warp yarns 42 a, 42 b. Warpyarn 44, when in the base layer 60, is in-phase with base warp yarn 42a, and out-of-phase with base warp yarn 42 b.

First warp yarn spacing 56 designates the space between adjacent basewarp yarns 42 a, 42 b in the base layer 60 when additional warp yarnsare not interwoven between the base warp yarns 42 a, 42 b with a weavepattern consistent with the base warp yarns 42 a, 42 b. Second warp yarnspacing 59 designates the larger center to center distance betweenadjacent warp yarns 42 a, 42 b in the base layer 60 to the right ofportion 46 where the yarns 42 a, 42 b been shifted apart.

FIG. 6 illustrates a side view of portion 46 of external surface 28,taken through lines 6-6 in FIG. 5. FIG. 6 illustrates how warp yarn 44floats over five weft passes 52 as a velour warp yarn, engage, i.e.,pass under, an additional weft pass (the sixth from the left), andchange weave patterns to adopt a base weave pattern by floating aboveand below consecutive weft passes. While FIG. 6 demonstrates a gap orspacing 65 between warp yarn 44 and the base warp yarns 42 when warpyarn 44 is not in the base layer 60, the warp yarn 44 may be woven in amanner such that no space or gap exists. Also, while FIG. 5 illustratesthe warp yarn 44 only projecting from surface 28 (an outer surface ofthe prosthesis 10), the velour warp yarn 44 may be flipped such that itprojects only from an inner surface of the prosthesis, or optionallyfrom both the inner and outer surfaces 26, 28. Further, while a floatover five weft passes is illustrated other floats may be used as well.

FIG. 7 illustrates a cross sectional view taken through lines 7-7 ofFIG. 6. First base warp yarn 42 a and second base warp yarn 42 b areshown to have different elevations, with a weft pass disposedtherebetween, but they may also be arranged so as to be at the sameelevation. A dashed line is included in FIG. 7 for illustrative purposesto distinguish between the base layer 60 below the dashed line and thenon-base layer 62 above the dashed line.

As indicated above, base warp yarns 42 a, 42 b and the interposed weftpasses 52 form the base layer 60 further illustrated in FIG. 7 andlateral distance 56 represents the center-to-center distance between thefirst and second warp yarns 42 a, 42 b. This distance 56 (see also FIG.5) between adjacent warp base warp yarns may be adjusted, e.g., so as tomake space for one or more velour warp yarns to be incorporated into thebase layer 60 and adopt a weave pattern consistent with the base layer60. To the extent desirable, e.g., to control porosity, suture retentionstrength, or permeability to blood of the prosthesis, distance 56 mayalso be decreased when a base warp yarn moves out of the base layer 60and adopts a weave pattern consistent with a non-base weave pattern,such as a velour weave pattern.

Warp yarns may be systematically moved from a first position in anon-base layer 62, hence outside of base layer 60 of the wovenstructure, to a second position within the base layer 60. In the firstposition, the warp yarns are woven in a manner in which they engage weftpasses, and may for example be woven in a velour-type manner, floatingover a plurality of weft yarn passes, adopting a non-base 62 weavepattern such as a velour weave pattern. Alternatively, in the firstposition, the warp yarns may be woven in a layer not in the base, suchas in a multi-layered or three dimensional fabric structure, wherein thebase comprises one of the layers, and the other layer(s) may comprisethe non-base layer 62. In the second position, the warp yarns are woveninto the base layer 60, preferably in a manner whereby the warp yarnsadopt or take on the weave pattern of the base 60.

When the warp yarns are moved into the base of the woven structure, someor all of the base warp yarns may be moved laterally with respect toeach other so that the warp yarn brought into the base has sufficientspace to adopt a weave pattern consistent with the base, and alsoprovide for a controlled base warp yarn density (e.g., a consistent warpyarn density). Warp yarn density is typically measured in warp yarns pergiven unit of length of fabric. For clarity, in the present disclosure,woven yarn density will relate to a given length of the woven structurethat can be measured for instance in a generally taut state, i.e., drawntight sufficient to remove slack. The density is measured as thequantity of yarns per given unit of length.

FIG. 8 illustrates an example embodiment of woven prosthesis 10′ of thepresent invention. Similar to FIG. 1, the prosthesis 10′ is illustratedas having a first tubular portion 12,′ a second bulbous portion 14,′ anda third portion 16.′ The second tubular portion 16, 16′ has a crimpedsurface 17, 17′ but may also be non-crimped. The crimped surface 17,17′can be circularly crimped, helically crimped, or configured withcombinations thereof.

FIG. 9 is a magnified view of a portion of the prosthesis 10′ takenabout a dashed line border 240. As can be seen in FIG. 9,circumferentially spaced velour warp yarns 44′ are woven into theprosthesis 10′ and extend longitudinally along the prosthesis 10.′ Thecircumferential center-to-center spacing of the velour warp yarns 44′ isadjustable. Also adjustable, is the pattern in which the velour warpyarns 44′ are longitudinally transitioned into and out of the base layer60 (FIGS. 12A-12C).

A plurality of groups of velour warp yarns (250, 254, 258, 262, 266, and270) are shown in FIG. 9. Each group is representative of a plurality ofwarp yarns that share a characteristic relating to the positioning ofthe groups of warp yarns. Shown for example in FIG. 9 are a plurality ofgroups, three of which are illustrated with suffixes a through c for thegroups of velour warp yarn 250, 254, 258, 262, 266, and 270. A firstgroup of velour warp yarns 250 is represented by velour warp yarns (orsets of velour warp yarns) 250 a, 250 b, and 250 c. These yarns may bebrought into the base and adopt a weave pattern consistent with the baseat the same or similar time during the weaving process. Subsequent tovelour warps yarns 250 a, 250 b, and 250 c being moved into the base,additional velour warp yarns such as a second group of warp yarns 254comprised of velour warp yarns 254 a, 254 b, and 254 c may be broughtinto the base. The process of moving one or more groups of velour warpyarns into the base intentionally correlates to the vertical positioningof reed 120 and can be used to maintain base warp yarn density, andcontrol the diameter of the prosthesis such as to increase or decreasethe diameter. This process as applied to groups of velour warp yarns 250and 254 can be subsequently adapted to additional groups, such as 258,262, 266, and 270. This process, therefore, can be used to controllablyexpand the diameter.

FIG. 10 is a magnified view of a portion of the bulbous section 14′shown in FIG. 9 and circumscribed by dashed line border 242 forillustration purposes. The portion circumscribed by dashed border 242includes one of the many velour warp yarns 44′ spaced about and woveninto prosthesis 10.′ In the magnified view of FIG. 10, it can be seenthat the portion circumscribed by border 242 actually includes twovelour warp yarns 272 b,′ 272 b″ that are closely spaced. FIG. 11 is amagnified view of the portion of the prosthesis 10′ circumscribed bydashed border 244

FIGS. 12A, 12B, 12C are sectional views shown in FIG. 10 taken alonglines 12A-12A, 12B-12B, and 12C-12C, respectively. For illustrativeclarity, the weft yarns are not shown. As the prosthesis 10′ is woven,and as further detailed below, velour warp yarns 272 b,′ 272 b″ areprogressively shifted from the velour layer 62,′ 62,″ 62′″ into the baselayer 60,′ 60,″ 60,′″ e.g., so as to maintain a warp yarn density of thebase layer 60 while increasing a width 108,′ 108,″ 108″′ defined by afirst set of warp yarns 84, 88, 90, 92. This can be used in a repetitivemanner throughout a prosthesis, to thereby produce a large diameterbulbous portion (such as bulbous portions 14, 14′ illustrated in FIGS. 1and 8), as well as manage porosity, warp yarn density, or otherproperties of a prosthesis.

Shown in FIG. 12A are a first set of warp yarns 112′ with six warp yarnsin the set, however other quantities are possible. First set of warpyarns 112′ has a plurality of base warp yarns 84, 88, 90, 92 in a base60′ thereby defining a first subset 106.′ Additionally shown in anon-base layer, such as a velour layer 62,′ are one or more velour warpyarns 272 b,′ 272 b.″ Flanking or adjacent to each side of the first setof warp yarns within border 112′ are additional base warp yarns 100,102. Two warp yarns within the first subset of warp yarns circumscribedby border 106,′ are spaced apart from each other a first distance 108,′a distance greater than the distance of any other pair of base warpyarns in the first subset circumscribed by border 106.′

Pertaining to the warp yarns of FIG. 12A, a warp yarn guide device, suchas a fan-shaped reed 120,′ may be used to control warp yarn spacing. Asshown in FIG. 14A, fan shaped reed 120′ has, e.g., three positions (122,124, and 126) where warp yarns intersect the reed 120′ to controlspacing during weaving. Correlating to the warp yarns arranged in FIG.12A, the position of fan shaped reed 120′ to facilitate the weavepattern of FIG. 11A is shown to be in a “high” position whereby the 120′reed engages warp yarns at a low location 126. The reed 120′ isprogressively lowered (or raised depending on its orientation) so as toshift the base warp yarns 84, 88, 90, 92 apart making space for thevelour warp yarns 272 b,′ 272 b″ to be incorporated into the base layer60,′ 60,″ 60.′″

Shown in FIG. 12B is the first set of warp yarns from FIG. 12A with adifferent arrangement and circumscribe by dashed border 112.″ The firstset of warp yarns in FIG. 12B differs from that of FIG. 12A in thatvelour warp yarn 272 b′ has been shifted into the first subset 106″orbase layer 60.″ Therefore, in the first subset 106″ of the first set ofwarp yarns circumscribed by dashed border 112,″ there are now five basewarp yarns instead of four. Reed 120″ may be shifted to the middleposition to shift the base warp yarns sufficiently to accommodate velourwarp yarn 272 b′ in the base layer 60.″

Reed 120″′ may be shifted even further to the low position illustratedin FIG. 14C so as to allow for incorporation of velour yarn 272 b″ to beincorporated in base layer 60,″′ as illustrated in FIG. 12C. In thisstate, the base layer 60″′ circumscribed by dashed line 106″′ holds sixbase warp yarns

The distance 108″′ shown in FIG. 12C has increased to be greater thandistances 108′ and 108″ shown in FIGS. 12A and 12B, respectively. Eventhough the distance 108″′ has increased, the warp yarn density of thebase layer 106″′ is maintained relatively consistent with the warp yarndensities of one or both of the arrangements depicted in FIGS. 12A and12B. Additionally, the velour warp yarn density in terms of velour warpyarns per given length, has decreased in FIG. 12C, i.e., to a magnitudeof zero) when compared to one or both of FIGS. 12A and 12B. Warp yarn272 b″ adopts the weave pattern of the base warp yarns circumscribed byborder 106″′ depicted in FIG. 12C.

The warp yarns are guided by reed 120 through a variety of spacings (ordents) within the reed used to influence the woven width (or diameter)of the prosthesis 10.″ As illustrated in FIG. 18, the spacings correlatewith locations 800, 802, 804, 806, 808, 810, and 812, each locationhaving a different offset (816, 818, 820,822, 824, 826, and 828)respectively, from a datum 814 on the reed 120. For example, since warpyarn group 250 is shown to enter the base layer first (from the bottomor distal end 20′ in FIG. 9), the portion of the prosthesis woven priorto group 250 being moved into the base relates to location 800 of fanshaped reed 120 spaced from a datum 814 on the reed a distance 816. Whenwarp yarn group 250 moves into the base layer, the fan shaped reed movesto a second position causing warp yarns to engage a second location 802on the fan shaped reed 120, spaced a distance 818 from the datum 814 onthe reed. This relationship may continue for the remaining groups 254,258, 262, 266, and 270 such that portions of the bulbous profile 230′ inFIG. 9 can be controllably and repeatably formed.

In order to achieve both a flare and a taper, the process describedabove to expand the diameter can be reversed while still weaving in thesame warp yarn direction. Therefore, warp yarns are shifted from a baselayer into a non-base layer such as a velour layer when a taper isdesired. The fan shaped reed will therefore be controlled to move in theopposite direction, causing the diameter of the bulbous portion 14′ ofprosthesis 10′ to be reduced, thereby controllably forming the contour232′ illustrated in FIG. 9.

While FIGS. 12A through 12C illustrate a specific behaviour of a set ofwarp yarns applicable to many different woven structures, such as awoven conduit, the principles illustrated in FIGS. 12A through 12C maybe replicated throughout portions of woven structures, including wovenstructures configured to be used as vascular prostheses, e.g., in whichcomplex and varied diameters or contours are desired. Contoured shapesincluding cylindrical conduits may be formed and configured to representthe natural geometries and shapes of the vascular structure for humansand mammals. This can be accomplished without using yarns of differentmaterial attributes, such as shrinking attributes, includingcoefficients of shrinking. In alternative embodiments however, yarns ofdifferent coefficients of shrinking may be used.

Prosthesis 10′ of FIG. 8 has a length 220 between twelve and thirtycentimeters, although other lengths may be appropriate depending on theintended use. The second tubular portion 16′ has a first length 218greater than ten centimeters, preferably fifteen centimeters, but otherlengths may be used. The first tubular portion 12′ has a first tubulardiameter 222 and a length 212, and the second tubular portion 16′ has asecond tubular diameter 224. A maximum diameter 226 is greater than thediameters of the first and second tubular portions 12′ and 16′respectively, and is positioned within the bulbous portion 14.′ Themaximum diameter 226 is larger than the diameters 222 and 224 by four tosixteen millimeters, preferably six to ten millimeters, and mostpreferably by about eight millimeters, but this difference may bevaried.

As further illustrated in FIG. 8, the maximum diameter 226 of bulbousportion 14′ may be positioned to be closer to a first transition region22′ than a second transition region 24,′ hence further from the secondtransition region 24′ than the first transition region 22.′ For example,the maximum diameter 226 may be positioned at a distance 216 from secondtransition region 24,′ such that the distance 216 is between 50% and75%, or between 60% and 70%, or between 65% and 70% of the length 214 ofthe bulbous portion 14.′ The woven length 214 of the bulbous portion 14′is configured to approximate the diameter 224 within a tolerance of plusor minus two millimeters, preferably one millimeter. The first tubularportion 12′ is configured to have a length 212 measured from the firsttransition region 22′ to the proximal end 18,′ greater or equal to onecentimeter. All of these dimensions are provided as examples, for theymay vary, and they not intended to limit the scope of the invention.

The first transition region 22′ represents the transition from the firsttubular portion 12′ to the bulbous portion 14,′ while the secondtransition region 24′ represents the transition from the bulbous portion14′ to the second tubular portion 16′. The bulbous portion 14′ is wovento have a varied diameter profile and is configurable to have varyingdegrees of flaring and tapering, to mimic the natural anatomy, shape,dimensions, and intended blood flow dynamics of the aortic root forcardiothoracic surgery pertaining to the ascending aorta.

FIG. 9 illustrates a partial view of a woven prosthesis 10′ embodimentrepresentative of elements of the present disclosure, taken about border240 of FIG. 8. Illustrated in FIG. 9 is a bulbous portion 14,′ andadjacent thereto portions of the first tubular portion 12′ and thesecond tubular portion 16.′ Preferably, the first tubular portion 12′and the second tubular portion 16′ have warp yarns continuously woventhroughout the bulbous portion 14′ into one, preferably both of thefirst and second tubular portions 12′ and 16.′ Other elements such asfirst transition region 22′ and second transition region 24′ areillustrated as well. The second transition region 24′ may correlate withthe sinotubular junction common to the anatomy of the ascending aorta.

The velour warp yarn density (quantity of velour warp yarns per givenlength of woven fabric) is shown to decrease when moving towards themaximum diameter portion of the bulbous portion 14,′ and away fromeither the first or second transition regions 22′ and 24.′

Additionally shown in FIG. 9, the second tubular portion 16′ has acrimped surface 17.′ This is shown more specifically in FIG. 15, takenabout border 19 shown in FIG. 8. The crimped surface can be circularlyor helically crimped.

Variations of the shape illustrated in FIG. 9 can be made, bycontrolling how many warp yarns are moved into the base, as well ascontrolling the movement and coordination of the fan-shaped reed 120.Additionally, variations can be made by controlling how many weft passeswill be woven with the warp yarns while the fan-shaped reed 120 ismoving or stationary.

FIG. 11 illustrates the behaviour of the velour warp yarns 272 b′ and272 b″ circumscribed by border 244 in FIG. 10. Velour warp yarns 272 b′and 272 b″ are shown to adopt a 5/1 weave pattern in portion 780. Thevelour warp yarns 272 b′ and 272 b″ float over a plurality of weftpasses 752 (depicted as yarns extending from left to right in FIG. 11).After floating over weft pass 765 and under weft pass 766, velour warpyarn 272 b′ is shown to adopt the weave pattern of base layer 60,″ 60,″′which in this example may be represented as a 1/1 weave pattern.Thereafter, velour warp yarn 272 b′ engages each of the weft passes 769through 773. Fan shaped reed 120 adjusts from a first position 121′illustrated in FIG. 13A while weaving portion 780 to a second position121″ illustrated in FIG. 13B while weaving portion at or near transitionpoint 786 (illustrated by a dashed horizontal line). In the firstposition (FIG. 13A) where the reed 121′ has been moved to a topposition, warp yarns engage the reed at a low portion 136 of the reed,and in the second position 121″ (FIG. 13B), the reed has been moved to amiddle position whereby warp yarns engage the reed at the middle portion134 of the reed 121.″ Therefore, when velour warp yarn 272 b′ adopts thebase weave pattern 60,″ 60,″′ the warp yarn spacing in the base layer60,″ 60″′ may be maintained.

Further illustrated in FIG. 11, velour warp yarn 272 b″ is shown tofirst adopt a 5/1 weave pattern in portion 780 and part of portion 781,and then adopt a weave pattern consistent with the base weave pattern inportion 782. This behaviour is similar to that of velour warp yarn 272b,′ but begins at a different weft pass. After floating over weft pass766 and under weft pass 767, velour warp yarn 272 b″ is shown to adoptthe weave pattern of a base layer 60,″′ which in this example may berepresented as a 1/1 weave pattern. Similar to velour warp yarn 272 b,′velour warp yarn 272 b″ engages each of the weft passes 769 through 773.Fan shaped reed 120 adjusts from a second position 121″ illustrated inFIG. 13B to a third position 121″′ illustrated in FIG. 13C at or neartransition point 788 (illustrated by a dashed horizontal line). In thesecond position 121″ (FIG. 13B), where the reed 121″ has been moved to amiddle position, warp yarns engage the reed at a middle portion 134 ofthe reed, and in the third position 121″′ (FIG. 13C), the reed 121 ″′hasbeen moved to a bottom position whereby warp yarns engage the reed 121″′at the top portion 132 of the reed 121.″′ Therefore, when velour warpyarn 272 b″ adopts the base weave pattern, the warp yarn spacing in thebase layer 60″′ may be maintained, and the overall width achieved by thesame quantity of warp yarns from portion 780 has increased toincreasingly wider portions 781 and 782.

A distance between the two outer most base warp yarns 100 (on the farleft) and 92 (on the far right) increases in portion 781 and again in782 while the woven portion circumscribed by border 244 maintains afairly consistent warp yarn density.

FIG. 20 illustrates another example embodiment of the present invention.Prosthesis 310 comprises a proximal end 318, and a distal end 320, and asidewall 330 disposed therebetween, preferably constructed through aweaving process. The sidewall 330 may be woven with a base layer andvelour layer, as illustrated by example in FIGS. 12A through 12C. Suchweaving processes used to provide prosthesis 310 may be consistent withthe weaving of portions of prosthesis 10′ described herein.

Prosthesis 310 is configured to have a size and shape in accordance withthe bulbous portion of prosthesis 10.′ Unlike prosthesis 10,′ prosthesis310 does not have first and second tubular portions 12,′ 16.′ Prosthesis310 may be woven in a manner generally consistent with prosthesis 10.′Prosthesis 310 may be formed, for example, by cutting the bulbousportion 14′ from prosthesis 10,′ and utilizing the woven bulbous portionalone.

FIG. 21 illustrates a prosthesis 410 including a proximal end 418, and adistal end 420, and a sidewall 430 disposed therebetween, preferablyconstructed through a weaving process. The sidewall 430 may be wovenwith a base layer and velour layer, as illustrated by example in FIGS.12A through 12C. Such weaving processes used to provide prosthesis 410may be consistent with the weaving of portions of prosthesis 10′described herein.

Prosthesis 410 is configured to have a size and shape in accordance withthe bulbous portion of prosthesis 10,′ as well as the first tubularportion 12′ of prosthesis 10.′ Unlike prosthesis 10,′ prosthesis 410does not have a second tubular portion 16.′ Prosthesis 410 may be wovenin a manner generally consistent with prosthesis 10.′ Prosthesis 410 maybe formed by removing through cutting for instance, second tubularportion 16′ from prosthesis 10,′ and utilizing the remaining portion ofprosthesis 10′ not removed.

FIG. 22 illustrates a prosthesis 510 which comprises a proximal end 518,and a distal end 520, and a sidewall 530 disposed therebetween,preferably constructed through a weaving process. The sidewall 530 maybe woven with a base layer and velour layer, as illustrated by examplein FIGS. 12A through 12C. Such weaving processes used to provideprosthesis 510 may be consistent with the weaving of portions ofprosthesis 10′ described herein.

Prosthesis 510 is configured to have a size and shape in accordance withthe bulbous portion of prosthesis 10,′ as well as the first tubularportion 12′ of prosthesis 10.′ Unlike prosthesis 10,′ prosthesis 510does not have a second tubular portion 16.′ Prosthesis 510 may be wovenin a manner generally consistent with prosthesis 10.′ Prosthesis 510 maybe formed by removing through cutting for instance, second tubularportion 16′ from prosthesis 10,′ and utilizing the remaining portion ofprosthesis 10′ not removed.

FIG. 23 illustrates a prosthesis 610 which comprises a proximal end 618,and a distal end 620, and a sidewall 630 disposed therebetween,preferably constructed through a weaving process. The sidewall 630 maybe woven with a base layer and velour layer, as illustrated by examplein FIGS. 12A through 12C. Such weaving processes used to provideprosthesis 610 may be consistent with the weaving of portions ofprosthesis 10′ described herein.

Prosthesis 610 is configured to have a size and shape in accordance witha portion of the bulbous portion 14′ of prosthesis 10,′ as well as thesecond tubular portion 16′ of prosthesis 10.′ Unlike prosthesis 10,′prosthesis 610 does not have a first tubular portion 12,′ nor does ithave a proximal portion of the bulbous portion 14′ of prosthesis 10.′Therefore, the bulbous portion of prosthesis 610 only expands outward inan increasing diameter configuration, such as a “flared” manner, flaringfrom the second tubular portion 616 towards the proximal portion 618.Prosthesis 610 may be woven in a manner generally consistent withprosthesis 10.′ Prosthesis 610 may be formed by removing through cuttingfor instance, the proximal portion of the bulbous portion 14,′ throughcutting for instance at the location of the maximum diameter 226 ofprosthesis 10′ (FIG. 8), as well as the first tubular portion 12′ ofprosthesis 10,′ thereby utilizing the remaining portions of prosthesis10′ not removed.

In order to accomplish the change in woven structure width along a weftyarn direction, or for tubular structures, the change in relateddiameters, the principles of weave pattern adjustment from a velour warpyarn to a base warp yarn, as described previously by example in relationto FIGS. 12A through 12C, and applicable to the finished prosthesesillustrated for example in FIGS. 1, 8, 9, and 20 through 23, will beillustrated and further described.

It should be noted that embodiments of the invention may involve allvelour warp yarns to move into the base as illustrated for example forprosthesis 10″ in FIGS. 16A and 16B only to emerge again. In otherembodiments, such as the prosthesis 10″′ illustrated in FIGS. 17A and17B, less than all of the velour warp yarns are moved into the base.

It should also be noted that many permutations of weave patterns may beemployed to carry out the invention. For example, warp yarns not in thebase may exist in a layer of a three dimensional fabric near or adjacentto the base, and then may be brought into the base. Alternatively, warpyarns not in the base may be of the many varieties of velour warp yarnssuch as single velour and double velour warp yarns. The single or doublevelour warp yarns may be brought into the base and adopt a weave patterninvolving a higher frequency of interlacing when in the base than whennot in the base. This may be fully or partially achieved by the movementof the velour warp yarns from a first position in which the velour warpyarn adopts a velour weave pattern, such as but not limited to a 5/1velour weave pattern, and adjusts to a second weave pattern, such as aweave pattern consistent with the base, including but not limited to a1/1, 6/4, or 6/3 weave pattern. Other weave patterns appropriate for thebase include, for example, a 3/1 weave pattern, a 2/1 weave pattern, a1/3 weave pattern, as well as a 1/4 weave pattern.

Additionally, it should be noted that by adjusting where the velouryarns transition into the base, the rate of expansion or contraction forthe width of woven structure will be controllable, and enable differentshapes and geometries to be fabricated.

Method of Manufacture And Fabrication

Prostheses consistent with and resulting from the methods of manufactureof the embodiments of the present invention may be constructed in avariety of specific ways. In certain embodiments, examples of thepresent invention may be manufactured in four steps comprising (i) aflat weaving step, (ii) a cutting step, (iii) a heat setting step, and(iv) a sterilization step. The heat setting step may be achieved in atwo-step manner, first involving the application of heat through acrimping mandrel to crimp and corrugate certain portions of the surfaceof portions of the prosthesis, as well as a shaping step in which heatis applied to the prosthesis, whereby the prosthesis takes a “set” or“shape memory” in an expanded state through the usage of an expandablebladder configured to provide a shape consistent with the desired finalshape of the prosthesis.

An example prosthesis according to the present invention, includingprosthesis 10, 10,″ 10,″′ may be woven with a loom, e.g., aJacquard-type loom 136, and a warp yarn guide device, e.g., fan-shapedreed 120, as shown in FIGS. 18, 19A, and 19B. The warp yarns or threads(i.e., those yarns extending in the longitudinal direction) and one ormore weft or fill yarns or threads (i.e., those yarns extendinggenerally transverse to the longitudinal direction of the portion to bewoven) are interlaced with one another in one or multiple predeterminedweaving patterns. When weaving a conduit, as employed in variousembodiments of the present invention, at the weaving station of theloom, the warp yarns are fed individually through heddles alignedtransverse to the longitudinal direction on one of four or more shafts.The upward and downward movement of the shafts moves a preselectedpattern of the warp yarns up and then down. In such an arrangement, twoof the shafts move the warp yarns for forming the upper surface of thetubular conduit, and two of the shafts move the warp yarns for formingthe lower surface of the tubular conduit. As the warp yarns on one shaftare drawn upwardly and the warp yarns on another shaft are drawndownwardly, the weft thread is shuttled in a first direction betweenthose groups of warp yarns to weave the upper surface of the tubularconduit, thereby providing a weft pass of the weft yarn, also known as amachine pick. The weft yarn is then shuttled in a reverse directionbetween another group of upwardly and downwardly drawn warp yarns toweave the lower surface of the tubular conduit, thereby creating anadditional weft pass or machine pick. The position of the shafts andthus the position of the warp yarns is then reversed and the weft threadis again shuttled between the groups of warp yarns, creating a pluralityof weft passes, wherein the process continues resulting in a woventubular shape.

As they approach the weaving station, the warp yarns are fed between thefingers of fan-shaped reed 120, which aligns the yarns for weaving andwhich thus determines the ultimate shape of the woven article. Wherebyweaving tubular articles having a substantially constant diameter isperformed utilizing a conventional front reed which is fixed in placeand which has evenly spaced fingers used to produce constant spacingbetween the warp yarns, reeds with varying spacing will be beneficialfor carrying out the present invention but are not required. An exampleof such a reed has spacing between the fingers which is narrow at afirst end or bottom end, and gradually increases toward the top end. Incontrast to conventional reeds, the fan-shaped reed 120 is not held in afixed position, but rather is moved upward or downward to alter yarn toyarn spacing in all or portions of the of the article being woven. Forexample, fan shaped reed 120,′ 120.″ 120,″′ as shown in FIGS. 14A-14C,may be moved upwards and downwards, causing warp yarns to engage the fanshaped reed 120,′ 120,″ 120″′ at a plurality of elevations representedby dimensions 816 through 828 in FIG. 18, all with respect to a datum134. When the fan shaped reed is at its highest position, the warp yarnsengage the reed at a low position such as that represented by location800 in FIG. 18. Likewise, when the fan shaped reed is at its lowestposition, the warp yarns engage the reed at a high location such as thatrepresented by location 812 in FIG. 18. In the context of fabricating atubular article consistent with certain embodiments of the presentdisclosure, the movement of the fan-shaped reed 120 provides for anadjustable diameter.

When programmed to coordinate with the specific manipulation orengagement of warp yarns, the spacing of warp yarns can be adjusted toprovide for sufficient space such that one or more velour warp yarns maybe brought into the base, and woven as a part of the base, therebyadopting a weave pattern consistent with the base. The invention therebyenables a base warp yarn density to be held within a range or otherwisemanaged, such that the diameter of a tubular woven conduit may beselectively adjusted, without requiring an adjustment of the finishedspacing of warp yarns within a base layer. Provided that a sufficientquantity of velour warp yarns are able to be brought into the base,controlled flaring and tapering of all or portions of a woven tubularconduit may therefore be provided

When the reed 120 is gradually moved upwards as the weaving of thetubular conduit advances, the spacing between the warp yarns and, hence,the diameter of the tubular article being woven, see, e.g., greige 130in FIG. 19A, will gradually be decreased. Similarly, when the reed 120is gradually moved downward as the weaving of the tubular conduitadvances, the spacing between the warp yarns will increase as will thediameter of the tubular article being woven. The rate of movement of thereed 120 will determine the taper of the article being woven, the fasterthe reed is moved, the larger the angle of taper, and the slower thereed is moved, the smaller the angle of taper. Moving the reed at aconstant rate will produce a constant angle of taper. However, changingthe rate of movement of the reed enables tubular articles to be formedwith curved or changing angles of taper. It is noted that use of thereed is not required as the spacing between warp yarns may already belarge enough to accommodate shifting of the non-base warp yarns, e.g.,velour war yarns, into the base layer of the prosthesis.

When using a movable reed 120, it is initially held in a fixed lowerposition to weave a substantially uniform diameter tubular conduit. Whena desired length of the tubular conduit has been reached, the reed 120is drawn downwards in increments, providing additional spacing betweencertain warp yarns such that additional warp yarns may be moved from afirst position in a velour layer to a second position in the base layer.This is done such that when the warp yarns are brought into the baselayer, and adopt a weave pattern consistent with the base layer, asillustrated in FIGS. 12B-12C, for example, the resulting spacing betweenthe warp yarns adjacent the additional warp yarn is increased. With eachchange for additional warp yarns to be brought into the base, themovement of the reed 120 will have to be evaluated to see if anadjustment is needed to provide sufficient spacing such that at a ratewhich would produce the desired angle of taper. The front reed iscontinued to be drawn downward as the weaving process continues until awoven fabric having the desired tubular configuration has been formed asthe greige 130 represented for example in FIGS. 19A and 19B.

The weaving step utilized to fabricate embodiments of the presentinvention may be conducted for a given length of a woven structure. Inaccordance with embodiments of the present invention, a plurality ofbulbous portions may be woven into a greige 130 shown in FIGS. 19A and19B. A secondary cutting step may be employed at cutting locations 132shown in FIG. 19A as dashed lines in order to section the wovenstructure to a length consistent with the desired intended usage of aprosthesis.

During further processing of the prosthesis, all or portions of theprosthesis of the present invention may be crimped to provide for “selfsupporting” qualities of the finished prosthesis, adding rigidity to thetubular prosthesis wherein the strength is needed to ensure proper crosssectional area for assured flow of blood through the conduits. Examplesare disclosed by example in U.S. Pat. No. 3,945,052 herein incorporatedby reference. As illustrated in all the figures, neither the bulbousportion nor the collar or first woven portion 12,12′ are crimped butthey may be crimped in other embodiments. A benefit to not crimpingthese sections include, for example, being able to provide a surgeonlocally flat or slightly curved surfaces beneficial for anastomosis andsuturing. Providing a surface that has crimps, pleats, or corrugationsin the bulbous portion 14, 14′ and/or a collar, e.g., the proximaltubular woven portion 12, 12,′ may complicate suturing and anastomosisprocedures as it is understood to be more convenient to suture andperform a proximal anastomosis on a flat or slightly curved surfacerather than a non-uniform crimped, pleated, or corrugated surface.

The woven fabric or prosthesis 10, 10,′ 10,″ 10″′ may be coated with acollagen or gel coating applied to entire length of the prosthesis forsealing purposes. Therefore, in addition to a uniform textile structuralporosity capable of being achieved in a base layer (between warp yarns,weft yarns, and interwoven combinations thereof), a uniform functionalporosity impacting permeability of the woven fabric to a fluid mayadditionally be achieved.

The prosthesis 10, 10,′ 10,″, 10″′ may be sterilized from any of thesterilization process suitable for woven grafts, including gammaradiation or cobalt 60 radiation, ethylene oxide gas, or e-beamradiation as commonly known to one skilled in the art.

Materials useful for forming embodiments of the present inventioninclude textile weaving products, for example, synthetic materials suchas synthetic polymers. Synthetic yarns suitable for use in the presentinvention include, but are not limited to, polyesters, includingpolyethylene terephthalate polyesters (herein referred to as PET),polypropylenes (herein referred to as PP), polyethylenes, polyurethanesand polytetrafluoroethylenes (herein referred to as PTFE). The yarns maybe of the monofilament, multifilament, spun type or combinationsthereof. The yarns may also be flat, twisted or textured, and may havehigh, low or moderate shrinkage properties. Such yarn materials, forinstance PET, are available from DuPont under the trade name of Dacron.The yarns may, for example, have a total denier in the range of 15 to300, or in the range 100 to 200, and may also be about 140 denier butcan have other sizes as well. The yarns may be comprised of single ormultiple plies. An example yarn that may be utilized according to thepresent invention may be texturized and PET based, and comprises twoplies, each having a denier of 70, the yarn having a total denier of140.

The following two examples are to be illustrative of embodiments thatrelate to the present invention. They both relate to the formation of abulbous prosthesis, consistent with prosthesis 10, 10′ shown in FIGS. 1and 8 respectively. Unless otherwise noted, the vascular prosthesis ofall of the following examples were fabricated through flat-wovenprocesses, arranged to achieve a tubular configuration using anelectronic Jacquard weaving machine and a variable reed such as afan-shaped reed.

EXAMPLE 1

In a first example of the present invention, an aortic prosthesis isconstructed to have small diameter of approximately 32 millimeters, anda maximum diameter of approximately 40 millimeters. The prosthesis isconstructed in accordance with the elements represented for instance inFIGS. 1 and 9.

A weft yarn material chosen for the present example is comprised ofpolyethylene terephthalate (PET) is provided having two plies of 70denier per ply, thereby having a final denier of 140. A warp yarnmaterial chosen for the present example is comprised of polyethyleneterephthalate (PET) and is provided having two plies of 70 denier perply, thereby having a final denier of 140. Either or both of the warpand weft yarn materials may be texturized or untexturized. A base weavepattern is chosen to be a plain weave pattern. It is determined that avelour layer will be woven to the outside of the base layer. The weavepattern chosen for the velour layer is a 5/1 pattern.

A constant weft yarn spacing is chosen to be used for the weaving of allwoven portions of the prosthesis. Specifically, a weft yarn spacing of66 yarns per inch (26 weft yarns per centimeter) is determined to beused for all woven portions of the prosthesis.

A total quantity of warp yarns is chosen based on a desired warp yarndensity, positioning, and finished diameters, including the maximumdiameter portion of the woven article. By way of example, a total of 703warp yarns have been chosen.

When weaving the first portion 12, 12′ and the third portions 16,16′(both collar and crimped/corrugated sections respectively), theposition of the reed 120 is set to its narrowest width in order toachieve a woven fabric tubular diameter of approximately 32 mm (or flatwidth 50.3 mm), and the total of 703 warp yarns are so divided into twogroups. The first group includes 469 warp yarns to form the base layer,and the second group includes 234 warp yarns to form the velour layer ofthe first portion. Therefore, to achieve the intended tubular diameterof 32 millimeters , the warp spacing for the base layer is 118 yarns perinch (46 yarns per centimeter) when a 32 millimeter diameter portion isto be woven, and 59 velour warp yarns per inch (23 yarns per centimeter)for the velour layer. The average fabric warp spacing including bothvelour and base warp yarns is the sum of both layers, i.e., 177 yarnsper inch (70 yarns per centimeter). The first tubular portion 12, 12′ iswoven with warp yarns acting as both base warp yarns and velour warpyarns to establish the first tubular portion 12, 12.′

The fan shaped reed 120 is gradually repositioned in steps during theweaving process to achieve the desired profile of the bulbous portion14, 14.′ This occurs in combination with the conversion of velour warpyarns into base warp yarns, until the maximum desired diameter isachieved.

When reaching the maximum diameter portion, the reed 120 is at itswidest to facilitate maximum fabric tubular diameter of 40 mm (or flatwidth 62.8 mm), and the total of 703 warp yarns are so divided into twogroups that 584 yarns now form the fabric base layer (for example, theinner surface), and 119 yarns form the velour layer or layers. As aresult, the warp spacing for the ground layer 60, 60′ is maintained as118 yarns per inch (46), while the velour layer is reduced to 24 yarnsper inch (9 yarns per centimeter) for the velour layer 62, 62.″

EXAMPLE 2

In a second example of the present invention, an aortic prosthesis isconstructed to have small diameter of approximately 24 millimeters, anda maximum diameter of approximately 32 millimeters. The prosthesis isconstructed in accordance with the elements represented for instance inFIGS. 1 and 9.

A weft yarn material chosen for the present example is comprised ofpolyethylene terephthalate (PET) is provided having two plies of 70denier per ply, thereby having a final denier of 140. A warp yarnmaterial chosen for the present example is comprised of polyethyleneterephthalate (PET) and is provided having two plies of 70 denier perply, thereby having a final denier of 140. Either or both of the warpand weft yarn materials may be texturized or untexturized. A base weavepattern is chosen to be a plain weave pattern. The velour layer 62, 62″can be woven to the outside of the base layer 60, 60.″ The weave patternchosen for the velour layer is a 5/1 pattern.

A constant weft yarn spacing is chosen to be used for the weaving of allwoven portions of the prosthesis 10, 10.′ Specifically, a weft yarnspacing of 66 yarns per inch (26 weft yarns per centimeter) isdetermined to be used for all woven portions of the prosthesis 10, 10.′

A total quantity of warp yarns is chosen based on a desired warp yarndensity, positioning, and finished diameters, including the maximumdiameter portion of the woven article. By way of example, a total of 550warp yarns have been chosen.

When weaving the first portion 12, 12′ and the third portion 16, 16′(both corrugated and collar portions), the position of the reed 120 isset to narrowest width in order to achieve a woven fabric tubulardiameter of approximately 24 mm (or flat width 37.7 mm), and the totalof 550 warp yarns are so divided into two groups. The first groupincludes 367 warp yarns to form the base layer 60, 60,″ and the secondgroup includes 183 warp yarns to form the velour layer 62, 62′ of thefirst portion 12, 12.′ Therefore, to achieve the intended tubulardiameter of 24 millimeters, the warp spacing for the base layer 60, 60′is 124 yarns per inch (49 yarns per centimeter) when a 24 millimeterdiameter portion is to be woven, and 62 velour warp yarns per inch (24yarns per centimeter) for the velour layer 62, 62.′ The average fabricwarp spacing including both velour and base warp yarns is the sum ofboth layers, (i.e., 177 yarns per inch, or 70 yarns per centimeter). Thefirst tubular portion 12, 12′ is woven with warp yarns acting as bothbase warp yarns and velour warp yarns to establish the first tubularportion 12, 12.′ Again, the reed 120 is gradually repositioned in stepsduring the weaving process to achieve the desired profile of the bulbousportion 14, 14.′ This occurs in combination with the conversion ofvelour warp yarns into base warp yarns, until the maximum desireddiameter is achieved.

When reaching the maximum diameter portion, the reed 120 is at itswidest to facilitate maximum fabric tubular diameter of 32 mm (or flatwidth 50.3 mm), and the total of 550 warp yarns are so divided into twogroups that 491 yarns now form the fabric base layer 60, 60′ (forexample, the inner surface), and 59 yarns form the velour layer orlayers 62, 62.′ As a result, the warp spacing for the ground layer 60,60′ is maintained as 124 yarns per inch (49 yarns per centimeter), whilethe velour layer 62, 62″ is reduced to 15 yarns per inch (6 yarns percentimeter) for the velour layer.

After the maximum desired diameter is achieved, the diameter of theprosthesis 10, 10′ is intentionally reduced or tapered by reversing thesteps used to create the increased diameter. Specifically, warp yarnsnow in the base 60, 60′of the prosthesis 10, 10′ are adjusted and movedout of the base 60, 60′ to behave and perform as velour warp yarns. Thespacing of the base warp yarns still within the base 60, 60′ areadjusted to accommodate the removal of the warp yarn from the base layer60, 60′ to the velour layer 62, 62,′ without significantly impacting thewarp yarn spacing within the base 60, 60.′

As many apparently widely different embodiments of the present inventioncan be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the specificembodiments thereof except as defined in the appended claims.

The invention claimed is:
 1. An implantable medical prosthesiscomprising: a woven base comprising base warp yarns interwoven with weftyarn passes, at least a portion of the warp yarns of the woven base arewoven to have a first frequency of interlacing, the woven base at leastpartially forming smaller and larger diameter portions of theprosthesis; and one or more velour yarns forming part of both thesmaller and larger diameter portions and interwoven with the weft yarnpasses to have a second frequency of interlacing that is smaller thanthe first frequency of interlacing; in at least a portion of the largerdiameter portion at least one of the one or more velour yarns that isinterwoven with the weft yarn passes with a second frequency ofinterlacing is incorporated into the woven base and is interwoven withthe weft yarn passes to have a frequency of interlacing that is smallerthan the second frequency of interlacing.
 2. The prosthesis of claim 1,wherein within the smaller diameter portion, the at least one of the oneor more velour yarns is not incorporated into the woven base and doesnot exhibit a weave pattern consistent with the woven base.
 3. Theprosthesis of claim 1, wherein a spacing between the base warp yarns ismaintained approximately the same in the smaller and larger diameterportions without adding additional warp yarns to the larger diameterportion beyond that in the smaller diameter portion.
 4. The prosthesisof claim 1, wherein an increase in diameter of the prosthesis going fromthe smaller diameter portion to the larger diameter is effected byincreasing spacing between the base warp yarns during weaving of theprosthesis.
 5. The prosthesis of claim 3, wherein the spacing betweenthe base warp yarns in the larger diameter portion is made smallerwithout reducing a diameter of the larger diameter portion by at leastone of the one or more velour yarns incorporated into the woven base ofthe larger diameter portion.
 6. The prosthesis of claim 1, wherein theprosthesis is a generally tubular graft and the larger diameter portionlies within a portion of the graft varying in diameter along alongitudinal axis of the graft and the smaller diameter portion lieswithin a portion of the graft having a generally uniform diameter. 7.The prosthesis of claim 1, wherein the prosthesis is a generally tubulargraft and the larger and smaller diameter portions lie within a portionof the prosthesis varying with respect to diameter along a longitudinalaxis of the graft.
 8. The prosthesis of claim 1, wherein in at least aportion of the smaller diameter portion the one or more velour yarnsexhibit a float that is entirely absent or smaller in the largerdiameter portion.
 9. The prosthesis of claim 1, wherein a spacingbetween the base warp yarns in the smaller diameter portion is within30% of the size of the spacing in the larger diameter portion.
 10. Theprosthesis of claim 1, wherein a quantity of the base warp yarns andvelour yarns is the same in the larger diameter portion as the smallerdiameter portion, and wherein the base warp yarns and the velour warpyarns are continuously woven between the smaller diameter portion andthe larger diameter portion.
 11. The prosthesis of claim 1, wherein theprosthesis comprises a secondary woven layer disposed over at least oneof the smaller and larger diameter portions, and wherein a portion of ayarn forming the secondary layer is incorporated into the base layer ofthe larger portion.
 12. An implantable medical prosthesis comprising: awoven structure comprising warp yarns interwoven with weft passes, allor a portion of the warp yarns together with the weft passes form awoven base of the woven structure; a first portion of the wovenstructure is woven with a first set of the warp yarns, a first subset ofthe first set of the warp yarns interwoven with the weft passes formsthe woven base in the first portion, two of the warp yarns in the firstsubset of the first set of warp yarns in the first portion are laterallyspaced apart from each other a first distance along a surface of theprosthesis, the first distance is greater than any spacing between anyother pair of warp yarns in the first subset of the first set of warpyarns in the first portion along the surface of the prosthesis; a secondportion of the woven structure is located within the medical prosthesisat a location longitudinally offset with respect to the first portion,the second portion is woven with the first set of the warp yarns, asecond subset of the first set of the warp yarns is interwoven with theweft passes and forms the woven base in the second portion, two of thewarp yarns in the second subset of the first set of warp yarns in thesecond portion are laterally spaced apart from each other a seconddistance along the surface of the prosthesis, the second distance isgreater than any spacing between any other pair of warp yarns in thesecond subset in the second portion along the surface of the prosthesis;wherein the second distance is greater than the first distance, and thenumber of warp yarns in the first subset is smaller than the number ofwarp yarns in the second subset.
 13. The implantable medical prosthesisof claim 12, wherein the portion of the warp yarns interwoven with theweft passes and disposed in the woven base are arranged in a base weavepattern, and another portion of the warp yarns not disposed in the wovenbase are velour warp yarns.
 14. The implantable medical prosthesis ofclaim 12, wherein the prosthesis is a generally tubular graft, the firstportion having a first diameter along a longitudinal axis of the graft,the second portion having a second diameter along the longitudinal axislarger than the first diameter.
 15. The implantable medical prosthesisof claim 12, wherein in the first portion of warp yarns not in the firstsubset forming the woven base exhibit a float that is entirely absent orsmaller in the second portion.
 16. The implantable medical prosthesis ofclaim 12, further comprising a first end and a second end, and whereinessentially all the warp yarns extend between the first and second ends.17. The implantable medical prosthesis of claim 12, wherein theprosthesis comprises a secondary woven structure disposed over at leastone of the first and second portions, wherein a portion of a yarnforming the secondary woven structure is incorporated into the wovenbase of the secondary portion.
 18. The implantable medical prosthesis ofclaim 12, further comprising a first end and a second end, and whereinessentially all the warp yarns are continuously woven between the firstand second ends.
 19. The implantable medical prosthesis of claim 12,wherein the first set of warp yarns is a quantity N, the first subset isa quantity of N-1, N-2, or N-3 and the second subset is a quantitylarger than the first subset.
 20. The implantable medical prosthesis ofclaim 19, wherein N has a value of six.
 21. The implantable medicalprosthesis of claim 16, wherein all the warp yarns are continuouslywoven with the weft passes between the first and second ends.
 22. Animplantable medical prosthesis comprising: a woven base comprising basewarp yarns interwoven with weft yarn passes, the base at least partiallyforming smaller and larger diameter portions of the prosthesis; and oneor more additional warp yarns forming part of and interwoven with theweft passes in both the smaller and larger diameter portions; in atleast a portion of the larger diameter portion but not the smallerdiameter portion at least one of the one or more additional warp yarnsincorporated into the woven base and exhibiting a weave pattern havingthe same frequency of interlacing as the woven base.
 23. An implantablemedical prosthesis comprising: a prosthesis comprising a woven base, thebase forming all or part of the sidewall of a proximal tubular portion,a larger diameter portion, and a distal tubular portion, the largerdiameter portion comprises a maximum diameter, the maximum diameter is 4or more millimeters larger than a measured diameter within the proximaltubular portion, the larger diameter portion has a length betweenseventy five percent and one hundred fifty percent of the measureddiameter within the proximal tubular portion, the proximal tubularportion and the larger diameter portion have a substantially uniformyarn to yarn spacing within the woven base for warp yarns woven withweft passes within the woven base; the prosthesis comprising a non-baselayer comprised of at least a portion of the warp yarns woven with weftpasses, wherein a density of the warp yarns within the non-base layer issmaller in the larger diameter portion than at least one of the proximaltubular portion and the distal tubular portion.
 24. The implantablemedical prosthesis of claim 23, wherein the weft passes are woven withthe same yarn material and shrinkage attributes throughout the proximaltubular portion, the larger diameter portion, and the distal tubularportion.
 25. The implantable medical prosthesis of claim 23, wherein theweft passes are woven with the same weft yarn throughout the proximaltubular portion, the larger diameter portion, and the distal tubularportion.
 26. The implantable medical prosthesis of claim 23, wherein thelarger diameter portion is seamlessly woven with the proximal tubularportion and the distal tubular portion.
 27. The implantable medicalprosthesis of claim 23, wherein the same quantity of warp yarns is usedto form the proximal tubular portion, the larger diameter portion, andthe distal tubular portion.
 28. The implantable medical prosthesis ofclaim 23, wherein the larger diameter portion is configured to bedimensionally stable under pressurized conditions of 120 millimeters ofMercury.
 29. The implantable medical prosthesis of claim 23, wherein thelarger diameter portion is configured to maintain its diameter underfluidic pressurized conditions of 120 millimeters of Mercury.
 30. Theimplantable medical prosthesis of claim 23, wherein the woven base atthe maximum diameter of the larger diameter portion is free of at leastone of corrugations, pleats, and crimps.
 31. The implantable medicalprosthesis of claim 23, wherein the larger diameter portion isdimensionally stable under pressurized conditions of 120 millimeters ofMercury.
 32. An implantable medical prosthesis comprising: a tubularstructure having a first open end and a second open end and a sidewalldisposed therebetween, the tubular structure comprising a large diameterportion (i) located along a length of the tubular structure but not atthe first open end, and (ii) tapering towards and the first open end; aportion of the tubular structure located between the first open end andthe large diameter portion has a diameter smaller than the diameter ofthe large diameter portion; wherein the sidewall of the tubularstructure comprises a plurality of warp yarns continuously woven with aplurality of weft yarn passes between the first and second open ends;and wherein a portion of the tubular structure tapering between thelarge diameter portion and the first open end in a direction towards thefirst open end has an increase in the ratio of warp yarns woven as avelour layer than a base layer.